- Argo (Ἀργώ in Greek) is a constellation that is not so much disused as dismantled. It was one of the 48 constellations known to Greek astronomers, as listed by Ptolemy in the Almagest, but the 18th-century French astronomer Nicolas Louis de Lacaille found it large and unwieldy and so divided it into three parts: Carina, the Keel or body; Puppis, the Poop (i.e. stern); and Vela, the Sails. Were the three parts to be reunited, the resulting figure would be almost 28% larger in area than the current largest constellation, Hydra.